Re: [CAD_CAM_EDM_DRO] Re: Bridgeport Boss 6 Stepper Motors

vavaroutsos wrote:

> Jon, I have no problems making the calculations for torque and power
> required based on ball screw efficiency, TPI, IPM rapids, etc. Where
> I fall short is in the machinist knowledge area. I don't have a good
> feel for how much force is required on the X, Y, and Z axis for a
> series 1 machine.

I used 1000 Lbs. as a wild guess at the required force, for acceleration,
friction and cutting forces combined. I tried to do a calculation on the
worst case cutting force that could be delivered to the workpiece, but
it seemed pretty crude. You can figure 1 HP as 550 Ft-Lb/Sec. A 1"
diameter tool has a 3.14" circumference, and at 60 RPM, it would be
moving at a tangential velocity of 3.14 IPS, or 0.262 FPS. So, 550 Ft-Lb/Sec
divided by .262 Ft/Sec = 2102 Lbs! Now, generally, you won't run a
1" tool at only 60 RPM, so these forces are almost certainly greater
than you will ever experience with a 1 Hp spindle motor, but they give
some idea of what the worst case could be.

> I was looking at some 400W, 3000RPM servos that would provide about
> 600lbs of force with 300 IPM rapids on a continuous basis with a 2:1
> reduction. These are roughly 1/2hp motors. Based on your success with
> 1/8hp motors I guess these are more than enough. Thanks for the info.

If those are 400W Continuous, you should be fine. If they are 400 W peak,
they are pretty marginal. I figure I am running about 1/2 Hp peak. Note
that the stock motors in Bridgeport's EZ-Trak servo machines are
about 1 Hp continuous, with rediculous peak ratings - something like 26
A at 140 V = 3640 W = 4+ Hp.

Jon